The present invention relates to continuous casting of steels and, more particularly, to an electromagnetic stirring unit for continuous casting of steels, having an electromagnetic stirring coil for floating non-metallic impurities and gases entrapped in the molten steel by electromagnetically stirring the molten steel in a mould to remove these impurities and gases.
Still more particularly, the invention is concerned with an electromagnetic stirring unit for a continuous steel casting mould, the unit constituting at least a part of the side wall of the mould.
The invention is also concerned with an electromagnetic stirring unit of the type mentioned above, in which the electromagnetic stirring coil is enclosed within a housing constructed to permit an easy mounting and dismounting of the electromagnetic stirring coil.
It is known to electromagnetically stir the molten steel in a mould so as to positively float and remove non-metallic impurities and gases contained therein to improve the surface quality of the cast strand. For instance, Japanese Patent Application No. 4241/1979 discloses a casting mold having means for effecting such electromagnetic stirring. FIG. 1 of the present application shows a conventional continuous steel casting mould equipped with an electromagnetic stirring means. In this known casting mould, an electromagnetic stirring coil 6' is disposed to extend over the entire length and height of at least one of the walls of the mould, as will be seen from FIG. 1. Cooling water is supplied from a water supply chamber 3' provided at a lower part of a casting mould cooling box 1' so as to flow upwards through the passages in the mould wall directly contacting the molten steel, and is discharged through a water discharge chamber 4' provided at the upper end of the cooling box 1'.
As disclosed by the present inventors in the specification of Japanese Patent Laid-open Application No. 64953/1980, it is desired to position the top end of the stirring coil as close as possible to the liquid steel level (meniscus) in the mould, in order to obtain cast strands having a superior surface quality.
On the other hand, the rate of operation of the mould having electromagnetic stirring means is lowered by various reasons such as the necessity for the inspection, maintenance and replacement of the parts of the electromagnetic stirring unit, besides the wear of the cooling wall of the mould which is usually made of copper plate due to its high heat conductivity.
In the conventional mould shown in Japanese Patent Application No. 4241/1979, as shown in FIG. 1, the mould wall 9' is attached to the mould side wall 7" opposite to the molten steel by means of a multiplicity of bolts 5' to form the water supply chamber, water discharge chamber and a chamber 2' for housing the electromagnetic coil. Therefore, even when the inspection or maintenance work is to be made solely for the electromagnetic stirring coil, it is necessary to remove all of the multiplicity of bolts 5' which are driven from the outside of the cooling box 1 into the mould cooling wall 9' across the chamber 2' housing the electromagnetic stirring coil. In addition, this work accompanies various troublesome tasks such as detaching and attaching of packing between the cooling box 1' and the mould cooling wall 9', packing between the cooling box 1' and the water supplying and discharge chambers 3', 4' as well as connecting and disconnecting of the water pipes. Thus, it is necessary to disassemble the entirety of the mould, solely for the purpose of inspection or maintenance of the electromagnetic stirring coil. Clearly, these troublesome tasks impractically lower the rate of operation of a continuous casting process using the mould.